Zooming of medical images

ABSTRACT

The invention relates to a system (100) for zooming an image displayed in a viewport, wherein the image comprises a plurality of regions, each region of the plurality of regions having a zoom function associated with the region, the system comprising an input unit (110) for receiving a region input for selecting a region of the plurality of regions and for receiving a zoom input for zooming the image, and a zoom unit (120) for zooming the image based on the zoom input, using the zoom function associated with the selected region. The zoom function associated with each region of the plurality of regions may be defined in any way deemed useful. For example, it may be defined in such a way that the selected region or an interesting portion of it is displayed in the viewport or, vice versa, the selected region or an interesting portion thereof is removed from the displayed view of the image. Advantageously, the user does not always need to precisely select the zoom center, as the application will select the zoom center, based at least on the selected region.

CROSS-REFERENCE TO PRIOR APPLICATIONS

This application is the U.S. National Phase application under 35 U.S.C.§ 371 of International Application No. PCT/IB2012/053269, filed on Jun.28, 2012, which claims the benefit of European Patent Application No.11171848.2, filed on Jun. 29, 2011. These applications are herebyincorporated by reference herein.

FIELD OF THE INVENTION

The invention relates to displaying medical images. Especially, itrelates to interactive zooming of images such as mammography images.

BACKGROUND OF THE INVENTION

Currently, zooming of images is implemented by providing an input forchanging the scale of the viewed area. Various implementations arepossible. For example, in a 2D image, the user may select the zoomcenter (i.e., a fixed point in the 2D image) and scroll the mouse wheelto magnify or reduce the image. For mammography, this is typicallycombined by the display of mirrored images and mirrored pan and zoomoperations as described in WO 2006/018816 entitled “Display system forthe evaluation of mammographies”. Two-dimensional (2D) image zooming canbe generalized to three-dimensional (3D) image zooming. For example, forperspective projection, the displayed images are zoomed when the cameramoves along the line towards one of the vanishing points. For orthogonalprojections, zooming is based on changing the scale in the planesperpendicular to the projection lines, i.e., perpendicular to theviewing direction.

The drawback of available zoom implementations is that, when a userviews an image region which is of interest to him, the zooming functiondoes not always keep that region in the display. The region may quicklydisappear from the display when the zoom center is fixed far away fromthe region of interest and the region of interest is close to the borderof a viewport for displaying the image. This problem is often addressedby selecting the zoom center in the center of the region of interest.However, this method fails when the region of interest is adjacent tothe border of the viewport.

SUMMARY OF THE INVENTION

It would be advantageous to have an improved system for zooming images,wherein an image region of interest can be seen in the viewport whilethe image is zoomed-in.

To achieve this, in an aspect, the invention provides a system forzooming an image displayed in a viewport, wherein the image comprises aplurality of regions, each region of the plurality of regions having azoom function associated with the region, the system comprising:

-   -   an input unit for receiving a region input for selecting a        region of the plurality of regions and for receiving a zoom        input for zooming the image; and    -   a zoom unit for zooming the image based on the zoom input, using        the zoom function associated with the selected region.

The zoom function associated with a first region of the plurality ofregions, said first region surrounding the viewport center, may bedefined, for example, in such a way that the center of the first regionis the zoom center of a first zoom function associated with the firstregion. The zoom center of a second zoom function associated with asecond region adjacent to the viewport border may be a point on theviewport border adjacent to the second region.

A person skilled in the art will understand how to interpret the zoomcenter for 2-dimensional and 3-dimensional images. For example, in thecase of 2-D images, the zoom center is a point in the image; in the caseof orthogonal projection images, the zoom center is a point in theprojection plane (viewing plane); for perspective images, the zoomcenter is the vanishing point.

In an embodiment of the system, the selected region is defined on thebasis of a viewport location comprised in the region input. Each regionof the plurality of regions may be defined as a portion of the viewport.The viewport location means a location in the viewport. This locationmay be defined by a point or a pixel, for example. The selected regionmay be the region of the plurality of regions which comprises theviewport location comprised in the region input.

In an embodiment of the system, the selected region is further definedbased on an image object displayed in the viewport and the spatialrelation between the viewport location and the object. This allowsdefining the selected region on the basis of the viewport as well as onthe basis of the image contents. For example, a borderline of the regionmay be defined by a contour for delineating the object.

In an embodiment, the system further comprises a segmentation unit fordefining the image object. The segmentation may be carried outautomatically, semi-automatically or manually.

In an embodiment of the system, the zoom center of the zoom functionassociated with a region of the plurality of regions is at a predefinedlocation within the region. For example, the zoom center may be the‘mass’ center or ‘inertia’ center of the region. This helps to keep theportion of the displayed image comprising the center and itssurroundings in the viewport. The skilled person will understand how tocompute the mass or inertia center of a region replacing mass by imageintensity.

In an embodiment of the system, the zoom function associated with theregion is a combination of a zoom, pan and/or rotation transformation.For example, the zoom center may be translated while the image isrescaled. Optionally, the displayed image may be rotated about the zoomcenter. In this way, interesting image features may be betterrepresented in the zoomed image.

In an embodiment, the system is further arranged for zooming a secondimage displayed in a second viewport, wherein

-   -   each region of the plurality of regions has a second zoom        function associated with the region for zooming the second        image, and    -   the zoom unit is further arranged for zooming the second image        based on the zoom input, using the second zoom function        associated with the selected region.

This is useful, for example, in mammography, where mirrored images ofthe right and left breast are displayed, each in its own viewport, andzoomed simultaneously based on a zoom input provided for the right orleft breast. The viewports may be combined into a single display area.

In an embodiment of the system, the second zoom function is based on thezoom function associated with the selected region in the image and a mapof the viewport into the second viewport, wherein the zoom center of thesecond zoom function associated with the selected region is obtained bymapping the zoom center of the zoom function associated with theselected region into the second viewport using said mapping. The secondzoom scale of the second zoom function is computed based on the zoomscale of the zoom function. For example, the two scales may beidentical.

Advantageously, the system of the invention may be used for digitalmammography.

In a further aspect, the invention provides an image acquisitionapparatus comprising an embodiment of the disclosed system.

In a further aspect, the invention provides a workstation comprising anembodiment of the disclosed system.

In a further aspect, the invention provides a method of zooming an imagedisplayed in a viewport, wherein the image comprises a plurality ofregions, each region of the plurality of regions having a zoom functionassociated with the region, the method comprising:

-   -   an input step for receiving a region input for selecting a        region of the plurality of regions and for receiving a zoom        input for zooming the image; and    -   a zoom step for zooming the image based on the zoom input, using        the zoom function associated with the selected region.

In a further aspect, the invention provides a computer program productto be loaded by a computer arrangement, comprising instructions forzooming an image displayed in a viewport, wherein the image comprises aplurality of regions, each region of the plurality of regions having azoom function associated with the region, the computer program product,after being loaded, providing said processing unit with the capabilityto carry out steps of an embodiment of the disclosed method.

It will be appreciated by those skilled in the art that two or more ofthe above-mentioned embodiments, implementations, and/or aspects of theinvention may be combined in any way deemed useful.

Modifications and variations of the image acquisition apparatus, of theworkstation, of the method, and/or of the computer program product,which correspond to the described modifications and variations of thesystem or of the method, can be carried out by a person skilled in theart on the basis of the description.

A person skilled in the art will appreciate that an image dataset in theclaimed invention may be a 2-dimensional (2-D), 3-dimensional (3-D) or4-dimensional (4-D) image dataset, acquired by various acquisitionmodalities such as, but not limited to, X-ray Imaging, ComputedTomography (CT), Magnetic Resonance Imaging (MRI), Ultrasound (US),Positron Emission Tomography (PET), Single Photon Emission ComputedTomography (SPECT), and Nuclear Medicine (NM).

The invention is disclosed in the independent claims. Advantageousembodiments are disclosed in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will become apparent from andwill be elucidated by means of the implementations and embodimentsdescribed hereinafter and with reference to the accompanying drawings,wherein:

FIG. 1 shows a block diagram of an exemplary embodiment of the system;

FIG. 2 shows regions of an image, defined on the basis of a partition ofthe viewport;

FIG. 3 shows regions of an image, defined on the basis of objectdelineation;

FIG. 4 illustrates an embodiment of the system for concurrently zoomingmirrored images of the right and the left breast;

FIG. 5 shows a flowchart of exemplary implementations of the method;

FIG. 6 schematically shows an exemplary embodiment of the imageacquisition apparatus; and

FIG. 7 schematically shows an exemplary embodiment of the workstation.

Identical reference numerals are used to denote similar parts throughoutthe Figures.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 schematically shows a block diagram of an exemplary embodiment ofthe system 100 for zooming an image displayed in a viewport, wherein theimage comprises a plurality of regions, each region of the plurality ofregions having a zoom function associated with the region, the systemcomprising:

-   -   an input unit 110 for receiving a region input for selecting a        region of the plurality of regions and for receiving a zoom        input for zooming the image; and    -   a zoom unit 120 for zooming the image based on the zoom input,        using the zoom function associated with the selected region.

The exemplary embodiment of the system 100 further comprises:

-   -   a segmentation unit 130 for defining the image object;    -   a control unit 160 for controlling the work of the system 100;        and    -   a memory unit 170 for storing data.

In an embodiment of the system 100, there are three input connectors181, 182 and 183 for the incoming data. The first input connector 181 isarranged to receive data coming in from a data storage means such as,but not limited to, a hard disk, a magnetic tape, a flash memory, or anoptical disk. The second input connector 182 is arranged to receive datacoming in from a user input device such as, but not limited to, a mouseor a touch screen. The third input connector 183 is arranged to receivedata coming in from a user input device such as a keyboard. The inputconnectors 181, 182 and 183 are connected to an input control unit 180.

In an embodiment of the system 100, there are two output connectors 191and 192 for the outgoing data. The first output connector 191 isarranged to output the data to a data storage means such as a hard disk,a magnetic tape, a flash memory, or an optical disk. The second outputconnector 192 is arranged to output the data to a display device. Theoutput connectors 191 and 192 receive the respective data via an outputcontrol unit 190.

A person skilled in the art will understand that there are many ways toconnect input devices to the input connectors 181, 182 and 183 and theoutput devices to the output connectors 191 and 192 of the system 100.These ways comprise, but are not limited to, a wired and a wirelessconnection, a digital network such as, but not limited to, a Local AreaNetwork (LAN) and a Wide Area Network (WAN), the Internet, a digitaltelephone network, and an analog telephone network.

In an embodiment of the system 100, the system 100 comprises a memoryunit 170. The system 100 is arranged to receive input data from externaldevices via any of the input connectors 181, 182, and 183 and to storethe received input data in the memory unit 170. Loading the input datainto the memory unit 170 allows quick access to relevant data portionsby the units of the system 100. The input data comprises the image data,the region input and the zoom input. Optionally, the input data maycomprise instructions for the segmentation unit 130. The memory unit 170may be implemented by devices such as, but not limited to, a registerfile of a CPU, a cache memory, a Random Access Memory (RAM) chip, a ReadOnly Memory (ROM) chip, and/or a hard disk drive and a hard disk. Thememory unit 170 may be further arranged to store the output data. Theoutput data comprises the zoomed image data. The memory unit 170 may bealso arranged to receive data from and/or deliver data to the units ofthe system 100 comprising the input unit 110, the zoom unit 120, thesegmentation unit 130, and the control unit 160, via a memory bus 175.The memory unit 170 is further arranged to make the output dataavailable to external devices via any of the output connectors 191 and192. Storing data from the units of the system 100 in the memory unit170 may advantageously improve performance of the units of the system100 as well as the rate of transfer of the output data from the units ofthe system 100 to external devices.

In an embodiment of the system 100, the system 100 comprises a controlunit 160 for controlling the system 100. The control unit 160 may bearranged to receive control data from and provide control data to theunits of the system 100. For example, after receiving a region input forselecting a region of the plurality of regions and a zoom input forzooming the image, the input unit 110 may be arranged to provide controldata “the input data has been received” to the control unit 160, and thecontrol unit 160 may be arranged to provide control data “zoom theimage” to the zoom unit 120. Alternatively, a control function may beimplemented in another unit of the system 100.

In an embodiment, the invention is used by a physician for viewing animage of the left breast. FIG. 2 shows the left breast image in aviewport. There are two image regions, first image region 1 and secondimage region 2, defined on the basis of a partition of the viewport by apartition line 20. Such definition of regions is useful in the case ofx-ray mammography, where the breast image is shown in the viewport in astandardized way. The first region 1 is located near the chest wall. Thesecond region 2 comprises the remaining part of the image, not includedin the first region 1. The user may use the mouse to provide the regioninput and the zoom input. In an embodiment, the user may move thepointer to point at a location in the image and click the mouse button,thereby selecting a viewport location. Further, the user may use themouse wheel to zoom in or out the image. If the selected location 211 isincluded in the first region 1, the first region 1 is selected and thezoom function is the function associated with the first region 1. Thezoom center of the zoom function associated with the first region 1 isat the location 212, which is the intersection of the horizontalcrossing the selected location 211 and the left viewport border line. Inthis way, the user can view an area of the breast tissue near the chestwall. If the user selects a location 22 in the second region 2, thesecond region 2 is selected and the zoom function is the functionassociated with the second region 2. The selected location 22 becomesthe zoom origin of the zoom function associated with the second region2.

In an embodiment of the system, the selected region is further definedbased on an image object displayed in the viewport and the spatialrelation between the viewport location and the object. This embodimentis illustrated in FIG. 3. There are three image regions 1, 2′ and 3′,defined on the basis of a partition of the viewport by a partition line20 and a partition curve 30. Such a definition of the regions is usefulin the case of x-ray mammography, where the breast image is shown in theviewport in a standardized way. The partition curve 30 may be definedrelative to the viewport. Alternatively, the partition curve may bedefined based on image segmentation by the breast skin shown in theimage displayed in the viewport. The segmentation can be performedmanually, semi-automatically or automatically. A person skilled in theart will be able to choose and implement a suitable segmentation method.

As in the previous embodiment illustrated in FIG. 2, the user may usethe mouse to provide the region input and the zoom input by, insuccession, moving the mouse pointer to point at a location in theimage, clicking the mouse button, thereby selecting the location, andfurther using the mouse wheel to zoom in or out the image. The zoomfunctions associated with regions 1 and 2′ are the same as describedabove for regions 1 and 2 in FIG. 2, respectively. A third zoom functionis associated with region 3′. If the selected location 311 is in thethird region 3′, the third region 3′ is selected and the zoom functionis the function associated with region 3′, the zoom center of this zoomfunction is at the location 312, which is a location defined by theintersection of the normal to the partition curve 30 crossing theselected location 311 and the partition curve. Thus, selecting alocation in the third region 3′, the user can zoom in an area of thebreast near the selected portion of the skin.

Optionally, the zoom center may be visualized by a marker as illustratedin FIGS. 2 and 3.

In an embodiment, the system 100 is further arranged for zooming asecond image displayed in a second viewport, wherein each region of theplurality of regions has a second zoom function associated with theregion for zooming the second image, and the zoom unit 120 is furtherarranged for zooming the second image based on the zoom input, using thesecond zoom function associated with the selected region. This isuseful, for example, in mammography, where mirrored images of the rightand left breast are displayed, each in its own viewport, and zoomedsimultaneously based on a zoom input provided on the basis of the rightor left breast. FIG. 4 shows the right breast image in the viewport 41and the left breast image in the second viewport 42. The viewports arecombined into a single display area. By providing a region input and azoom input for zooming the image, the second image is zoomedconcurrently with the image, using derived zooming parameters based onthe same inputs and the associated second zoom function.

In an embodiment of the system 100, the second zoom function is based onthe zoom function associated with the selected region in the image and amap of the viewport into the second viewport for mapping the zoom centerof the zoom function associated with the selected region into the zoomcenter associated with the second zoom function. This embodiment isillustrated also in FIG. 4, wherein the map is the mirror reflection ofthe viewport 41 over the ‘symmetry’ line 40 into the second viewport 42.The second zoom function is thus defined by the zoom center 421 which isthe mirror image of the zoom center 411.

Although the embodiments of the invention have been described withreference to x-ray mammography images, a person skilled in the art willunderstand that the invention is useful for interacting with otherimages. Examples of such images include, but are not limited to, MRIbrain scans and PET images of the lungs.

Those skilled in the art will further understand that other embodimentsof the system 100 are also possible. It is possible, among other things,to redefine the units of the system and to redistribute their functions.For example, there may be several segmentation units 130, eachimplementing a different segmentation technique. Although the describedembodiments apply to medical images, other applications of the system,not related to medical applications, are also possible.

The units of the system 100 may be implemented using a processor.Normally, their functions are performed under the control of a softwareprogram product. During execution, the software program product isnormally loaded into a memory, like a RAM or other non-transitory media,and executed from there. The program may be loaded from a backgroundmemory, such as a ROM, hard disk, or magnetic and/or optical storage, ormay be loaded via a network like the Internet. Optionally, anapplication-specific integrated circuit may provide the describedfunctionality.

An exemplary flowchart of the method M of zooming an image displayed ina viewport, wherein the image comprises a plurality of regions, eachregion of the plurality of regions having a zoom function associatedwith the region, is schematically shown in FIG. 5. The method M beginswith an optional segmentation step S05 for defining an object in theimage. Alternatively, or after the segmentation step S05, the method Mis arranged for performing an input step S10 for receiving a regioninput for selecting a region of the plurality of regions and forreceiving a zoom input for zooming the image. After the input step S10,the method M continues to a zoom step S20 for zooming the image based onthe zoom input, using the zoom function associated with the selectedregion. After the zooming S20 step, the method M terminates.

FIG. 6 schematically shows an exemplary embodiment of the imageacquisition apparatus IAA employing the system SYS of the invention,said image acquisition apparatus IAA comprising an image acquisitionunit IAA10 connected via an internal connection with the system SYS, aninput connector IAA01, and an output connector IAA02. This arrangementadvantageously increases the capabilities of the image acquisitionapparatus IAA, providing said image acquisition apparatus IAA withadvantageous capabilities of the system SYS.

FIG. 7 schematically shows an exemplary embodiment of the workstationWS. The workstation comprises a system bus WS01. A processor WS10, amemory WS20, a disk input/output (I/O) adapter WS30, and a userinterface WS40 are operatively connected to the system bus WS01. A diskstorage device WS31 is operatively coupled to the disk I/O adapter WS30.A keyboard WS41, a mouse WS42, and a display WS43 are operativelycoupled to the user interface WS40. The system SYS of the invention,implemented as a computer program, is stored in the disk storage deviceWS31. The workstation WS is arranged to load the program and input datainto memory WS20 and execute the program on the processor WS10. The usercan input information to the workstation WS, using the keyboard WS41and/or the mouse WS42. The workstation is arranged to output informationto the display device WS43 and/or to the disk WS31. A person skilled inthe art will understand that there are numerous other embodiments of theworkstation WS known in the art and that the present embodiment servesthe purpose of illustrating the invention and must not be interpreted aslimiting the invention to this particular embodiment.

It should be noted that the above-mentioned embodiments illustraterather than limit the invention and that those skilled in the art willbe able to design alternative embodiments without departing from thescope of the appended claims. In the claims, any reference signs placedbetween parentheses shall not be construed as limiting the claim. Theword “comprising” does not exclude the presence of elements or steps notlisted in a claim or in the description. The word “a” or “an” precedingan element does not exclude the presence of a plurality of suchelements. The invention can be implemented by means of hardwarecomprising several distinct elements and by means of a programmedcomputer. In the system claims enumerating several units, several ofthese units can be embodied by one and the same record of hardware orsoftware. The usage of the words first, second, third, etc., does notindicate any ordering. These words are to be interpreted as names.

The invention claimed is:
 1. A system for zooming an image displayed ina viewport, wherein the image comprises a plurality of regionspartitioning the viewport, the plurality of regions having a pluralityof associated zoom functions, respectively, associated with the regions,the system comprising: an input unit configured to receive a regioninput, including a location in the viewport, for selecting a region ofthe plurality of regions of the image, and to receive a zoom input forzooming the image according to the zoom function associated with theselected region, the selected region being the region of the pluralityof regions that includes the location in the viewport included in theregion input; and a zoom unit configured to zoom the image based on thezoom input, using the zoom function associated with the selected region.2. The system as claimed in claim 1, wherein the selected region isfurther defined based on an image object displayed in the viewport and aspatial relation between the location in the viewport and the imageobject.
 3. The system as claimed in claim 2, further comprising asegmentation unit configured to defined the image object.
 4. The systemas claimed in claim 1, wherein a zoom center of the zoom functionassociated with a region of the plurality of regions is at a predefinedlocation within the region.
 5. The system as claimed in claim 1, whereinthe zoom function associated with the region is a combination of a zoom,pan and/or rotation transformation.
 6. The system as claimed in claim 1,the system further being arranged for zooming a second image displayedin a second viewport, wherein each region of the plurality of regionshas a second zoom function associated with the region for zooming thesecond image, and the zoom unit is further arranged for zooming thesecond image based on the zoom input, using the second zoom functionassociated with the selected region.
 7. The system as claimed in claim6, wherein the second zoom function is based on the zoom functionassociated with the selected region in the image and a map of theviewport into the second viewport, wherein a zoom center of the secondzoom function associated with the selected region is obtained by mappinga zoom center of the zoom function associated with the selected regioninto the second viewport, using said mapping.
 8. An image acquisitionapparatus comprising a system as claimed in claim
 1. 9. A workstationcomprising a system as claimed in claim
 1. 10. A method of zooming animage displayed in a viewport, wherein the image comprises a pluralityof regions partitioning the viewport, the plurality of regions having aplurality of associated zoom functions, respectively, associated withthe regions, the method comprising: receiving a region input forselecting a region of the plurality of regions, the region inputcomprising a location in the viewport, the selected region being theregion of the plurality of regions that includes the location in theviewport included in the region input; receiving a zoom input forzooming the image according to the zoom function associated with theselected region; and zooming the image based on the zoom input, usingthe zoom function associated with the selected region.
 11. Anon-transitory computer readable medium storing a computer program,executable by a computer processor, to enable zooming an image displayedin a viewport, wherein the image comprises a plurality of regionspartitioning the viewport, the plurality of regions having a pluralityof associated zoom functions, respectively, associated with the regions,the computer program comprising: region input code for receiving aregion input for selecting a region of the plurality of regions in theviewport, the region input comprising a location in the viewport, theselected region being the region of the plurality of regions thatincludes the location in the viewport included in the region input; zoominput code for receiving a zoom input for zooming the image according tothe zoom function associated with the selected region; and zooming codefor zooming the image based on the zoom input; using the zoom functionassociated with the selected region.